An automatic level filling valve used in a rotary level filling machine allows a container to be filled with a product to a preset level. The filling valve has two concentric tubes with an outer tube surrounding an inner tube so that the outer tube can slide longitudinally along the inner tube. A first or product passage is provided for allowing product to flow into the container, which product passage can either be formed within the first inner tube or as a recess on the outer periphery of the inner tube. A second or vent passage for venting air from the container during a filling operation extends longitudinally through the inner tube.
The outer tube is joined to and supported by a compressible bellows. In a rest position of the filling valve, the outer tube is biased by the compressible bellows to close off both the product and vent passages.
During operation, when the tubes are inserted into the container, the container presses against a part of the outer tube to counteract the bias of the bellows—thereby causing the outer tube to slide along the inner tube to open the product and vent passages. This allows the product to flow through the product passage into the container while air in the container is displaced by the product and vented through the vent passage.
The level to which the container is filled is determined by the distance that the outer tube is inserted into the container. The filling operation automatically stops after the product level in the container rises sufficiently to cover and close off the vent passage, because the air in the container is trapped and can no longer be vented through the vent passage.
The pressure exerted on the product in the container at this stage is dependent on and a function of the head of fluid or liquid provided in a filling bowl above the filling valve. This pressure often results in the container volume increasing slightly because of swelling under pressure, which can be quite significant for more flexible containers. Subsequently, as the container is removed from the valve, the valve is closed and the pressure head removed from the container. This results in a “contraction” of the container when returning to its normal shape and a corresponding decrease in container volume, often leading to some of the product in the container being ejected through its mouth.
The pressure head can also cause some of the product to leak out between the outer tube and the bellows due to the product flowing through the bellows before entering the product passage.
In order to maintain hygiene, particularly when the product being filled is for consumption, the valve must be regularly cleaned. Ideally, to improve production time, the valve should be cleaned in place on the filling machine. In filling machines not having a bellows, the cleaning is done by flushing the valve with cleaning fluid in a reverse direction to the normal filling operation. However in valves with regular bellows (i.e. having a constant side wall thickness), this is not possible due to the bellows being “concertinaed” when opened. Some product is thus trapped within the folds of the bellows side wall, which prevents proper cleaning. Thus such valves need to be removed from the filling machine and dismantled to be properly cleaned.
It is an object of the invention to suggest a valve, which will assist in overcoming these problems.